I'll prove it to you.
Beginning with the left panel, we see the donors of the work. Apparently coming home from a stroll in 12 degree weather, the couple has opened their front door to the sight of the annunciation occurring in their living room. They've stumbled and fallen at the sight.
From there, we should go behind the couple, where we will encounter the creepiest guy in all of art historical lore:
That's right, ladies and gents: Boo Radley (OR the prophet Isaiah... whatever) apparently hangs out in Flemish gardens AND behind doors in homes in the deep South. (what a creep.)
Next we move to the central panel, where we spot many hilarious things. The most obvious and awesome of which, is the baby Jesus flying through the closed window on a ray of light.
Then we see the suicidally worshipful candle, who has self-extinguished at the thought of the mention of Christ's name (and immaculate appearance through the window.)
Lastly we have to ask ourselves: Why was Joseph so much older and more Mediterranean looking than his supposedly 12 year old, Northern European bride? Does this creep you out at all? I would probably feel uncomfortable hanging out with this couple. Just sayin.